German reference DE2909890 describes state of the art cable bushings for this type of application. The conventional device serves as a shield for conductor bundles that are fed through a wall. The bushings protect the cables from emitting or receiving electrical and electromagnetic waves of high frequencies. This device is provided with a frame which is inserted into a wall opening and which accommodates several filler pieces arranged in a matrix. Wherever cables are to be guided through the frame, the fillers are formed by two halves fitted together between which an opening is provided to accommodate the cable which is to be guided through. In the area located within the frame, the electric shield of the cable is exposed. The two halves surround the cable guided through them and are provided with a radial nose in the area of the exposed shield. This nose is in direct contact with the exposed cable shield and the end areas of the fitting halves, located at both sides of the radial nose, are in direct contact with the cable jacket. The fittings and filler pieces consist of an elastic material which incorporates aluminum particles. A clamping piece consisting of an elastic material is arranged in the center of the matrix of filler pieces and fittings. The clamping piece can be compressed by means of a screw bolt and interacting press plates in the axial direction of the bolt and pressed apart in the radial direction in order to clamp the filler pieces and fittings to the frame and the cables. This conventional bushing is complicated due to the number of components and the assembly process and therefore is rather costly. Costs are particularly high if only a single cable must be guided through an opening in a partition. A pre-assembly of this device by the cable manufacturer or harnessing company is not possible. If the screw bolt, the press plates and the interacting elastic fitting are eliminated for cost and space reasons due to the standard manufacturing tolerances, it is not possible to ensure a safe and consistent enclosure of both fitting halves around the exposed cable shield, which may result in electromagnetic leakage and interference.
DE-GM 7721692 describes a sleeve for guiding a cable through walls in a fireproof and gas-tight way. The sleeve consists of two sleeve parts which are separated in the longitudinal direction and consist of an elastic material which swells when exposed to heat. The inner circumferences of the sleeve halves are provided with a trough-like cavity filled with a sealing material such as caoutchouc.
DE-A-2558885 describes a cable inlet in installation housings provided with plate-shaped flanges which are mounted in an opening in the housing wall and through which sealing pieces are inserted which surround the cables and guide them through the housing wall. The sealing bodies are divided longitudinally by means of half shells which can be coupled to each other. They are held apart by coupling pieces arranged in the tangential direction and by outer securing rings. The securing rings consist of a plastic material and render it impossible to make contact with an exposed cable shield. The state of the art solution fails to provide for an electromagnetically tight guiding device through a partition opening.
There is a need for an improved cable bushing that is electromagnetically tight and is made in such a way that only a few inexpensive components are required and where the cable manufacturer or harnessing company may pre-assemble the component by connecting a cable terminated with electrical connectors at both ends.